Sexual risk-taking behavior in adolescence, including early initiation of sexual intercourse, engaging in unprotected sexual activity, and having sex with multiple partners, places adolescents at risk of a number of potential negative consequences. Short-term consequences include unintended pregnancy and STD infection (including HIV infection), and longer-term consequences include such outcomes as disruption of the adolescent's education, leading to diminished economic circumstances for both the adolescent and potential offspring, and poorer health outcomes for both the adolescent and offspring. Delaying initiation of sexual intercourse seems most effective at reducing negative outcomes, however, interventions designed to delay sexual initiation or increase condom use have had varied success. Interventions to reduce sexual risk among adolescents who have already initiated have produced mixed results. Given the early ages at which adolescents begin sexual intercourse, intervention prior to the onset of puberty, or in early adolescence, seems crucial. To develop such interventions, longitudinal study of factors in pre- and early-adolescence that influence sexual risk-taking is needed. This investigation takes advantage of an existing longitudinal data set ("Children's Conceptions of AIDS and Related Risky Behaviors" 2 R01 DA 07047-10) for which participants have been followed from elementary into high school. The parent study included repeated measures of sexual risk-taking, other health risk behaviors, such as substance use, and healthy behaviors, such as exercise in addition to measures of environmental, interpersonal, and cognitive factors thought to influence risk-taking. The sample for the longitudinal study is large (n=1,173), ethnically diverse, and has high follow-up completion rates (88 percent at Year 7). Using this data set, we will examine early factors contributing to sexual risk-taking and the ages at which these factors appear to be important.